SEA-FISHERIES LABORATORY. 245 



and external to the epibranchial arteries, receiving in 

 their course vessels conveying blood from the head and 

 brain, ^tnd enter the precaval veins at the dorsal and 

 anterior extremities of the latter. 



The Inferior Jugular Vein (V. Jag. 1 ) is an azygos 

 trunk running backwards under the ventral wall of the 

 pharynx immediately above the dorsal aorta. It then 

 passes upwards on the anterior wall of the pericardium, 

 and may enter either the right or left side of the sinus 

 venosus, though its ending on the right side seems to be 

 the more common one. 



The Hepatic Veins (V. hef.) are short wide trunks 

 coming from the liver, which penetrate the posterior wall 

 of the pericardium and enter the posterior part of the 

 sinus venosus. 



The Renal Portal System. — The afferent vessels of this 

 system are the parietal veins, the caudal vein and the 

 genital veins. The caudal vein (V. cd.) runs forwards 

 from the tail in the haemal canal immediately beneath 

 the dorsal aorta. It enters the kidney at the most dorsal 

 and posterior angle of the latter organ, and divides into 

 two vessels which run forwards in the kidney and break 

 up, but do not apparently anastomose with the cardinal 

 vein. A short venous trunk comes from each ovary (or 

 testis) and the adjacent portions of the body wall, and 

 enters the kidney on each side near the extreme ventral 

 tip of the latter organ. A series of veins from the muscles 

 of the trunk enter the dorsal portion of the kidney on each 

 side ; these are the parietal veins. One such vessel is 

 represented in fig. 22 as entering the anterior tip of the 

 head kidney. 



The efferent vessels of the system are the cardinal 

 veins, which run forward in the kidney. The right car- 

 dinal vein (V. card.) runs along the middle part of 



